With a recent reduction in size and an increase in capacity, a magnetic disk apparatus has become available for portable use and, accordingly, resistance to environmental conditions such as vibration and impact, temperature, and atmospheric pressure is required to be improved.
In order to increase a mechanical strength of a magnetic disk apparatus under a reduced pressure, conventionally the air-bearing shape of a slider has been improved or parameters of a suspension spring pressure have been optimized.
Further, in recent years, as a technique for responding to a reduction in the flying height of a head, there is available a technique of setting the flying height to a desired height by using a heater provided near a read/write element positioned at the end of a head slider.
As a conventional art relating to the present invention, there are known the following apparatuses: a control apparatus that checks a change in the flying height caused due to a difference in atmospheric pressure by detecting a data error rate to thereby control a heater; a magnetic recording apparatus that controls the flying height in association with temperature; and a magnetic recording apparatus that checks an abnormal flying height by detecting the output of a head (refer, e.g., to Patent Document 1: Japanese Laid-open Patent Publication No. 2007-310957, Patent Document 2: Japanese Laid-open Patent Publication No. 2005-158088, and Patent Document 3: Japanese Laid-open Patent Publication No. 2005-141798).
With an enlargement of application of a magnetic disk apparatus, the level of a market demand in terms of a reduced pressure condition has become higher. Concretely, reduced pressure condition corresponding to an altitude of 4000 m to 5000 m class (conventionally, 3000 m) is required. Therefore, the reduced pressure resistance of a magnetic disk apparatus needs to be improved. Further, at the same time, with an increase in recording density of the magnetic disk apparatus, the flying height of a head slider needs to be reduced. Considering production variations including relative height between the slider and disk or disk flatness, it has become difficult to respond to a change in the flying height caused due to a reduction in pressure by improving the air-bearing shape of the slider.
Further, in order to ensure reliability of the magnetic disk apparatus, a crucial failure such as occurrence of scratches on the surface of a disk or occurrence of stiction between the head and disk due to a reduction in the flying height of the slider under a reduced pressure needs to be avoided.